Electronic diplex keyer



3 Sheets-Sheet l mwmaju mmm 50mm+ i G. L. BREWER ELECTRONIC DIPLEX KEYER Sept. 16, 1952 Filed Nov. 26, 1948 INVENTOR E N R Q n A GENE L. BREWER Patented Sept. 16, 1952 UNITED STATES fiFFifiE j 2,s11,0s4 v s 3 ELECTRONIC DIPILEX KEYER s I Gene Brewer. WashingtomD. C. i e Application-November 2s, 194s, Serial Marianogtcaims. 015117840):

(Granted'imderthe-act of March 3, 1883,'as

amended April"30, 1928;' 370 OLG. 757) The invention described herein maybe manufactured and used layer for the Government of the United States for governmental purposes without the payment to me of any royalty thereon in accordance with the'provisions of theact' of'April 30, 1928 (Ch. 460-, 45 Stat. L. 467);

' This invention relates to electronic keyers, and more particularly tdelectronic keyers for use in diplex Teletype receivers where the start-stop principle is' employed.

In one diplex telegraph system a S-unit code is used with the charactersof one message being transmitted during the first half of each unit and characters of thev'other message being transmitted during the last half of each unit. At the receiver it is necessary not only to separate the half-units constituting the two messages but to lengthen them to'unit'length so they will operate a conventional Teletype 'machine. J It is an object of this invention to provid an electronic keyer without mechanical parts,

It is also an object of this invention to provide electronic circuits to separate-*parts'of'a diple'xp message using half-units and properly lengthen -It is a further object of this invention to provide'an electronic keyer including an oscillator which isnormally stopped but'vvfhich will start] operating atthe beginning of jeach character and? operate during the transmission. of each; char 1 acter; Other" objects and a-dvantag" s of this invention will appearffrom' the following specification taken in connection withfthe drawing in which,

Fig. 1 is a lolock diagram of acircuit embodying the principles of this invention.

Figse -and 2b are 'detailed'isch'ematic diagrams of a circuit embodying the' principles'of this invention.

Fig. 3 shows a series of graphs depicting the" signal occurring in various designated peints'of thecircuitshown'inFigl z.

This -invention contains features whereby the various electronic circuits are interdependent one upon another for timing and interlocking such thatmuch of the operation is referred to one multivibrator cir'cuitior timing. I

This invention further contains features whereby the incoming start pulse actuates an adjustable time delay or lag circuit which in turn starts the'electronic circuitswhich produce the sampling pulses for interrogating the intelligence pulses of theincoming signal. The lag circuit timing adjustment positions the train of sampling pulses with- -respect to the signal pulses in the same manner as the range arm control mechanical systems. I i

For general description of this invention, reference is had to Figs. 1 and 3 in which an audio tone-modulatedby groups of coded pulses is ap-- plied through an input amplifier and a signal rectifier to triggercircuits in which the coded pulses are reshaped into square'waves. Part of the output of the trigger circuits is applied to shaped coded pulses arrive in synchronism with the risingedge"of the square Wave from the multivibrator The other output of the frequency multivibrator is applied along with the reshaped coded pulses to the other clipper circuit whichpasses only those pulses which arrive "in synchroriism' with the rising edge of the square waveirom the multivibrator. One clipper circuit feeds its output pulses to the A regenerator circuit which-lengthens the pulses to, a time period or one simplexmnit. The other clipper circuit feeds intojthe B regenerator "circuits which also lengthens its received pulsesto a length ofone simplex unit. Regenerator, .cir

For :amore detailed description ofladevice eme I bcdylng' the principles of'this invention, refer ends is had to Figs; 2- 11. and 2-D wherethe input consisting 'offgro'ups or coded pulses eaten-m5 posed on an audio tone is 'appliedto; transformer T2. The output from transformer T2 is taken does in from an adjustable tap engaging resistor R1 connected across the secondary of the transformer.

The output of transformer T2 is connected through input amplifier tube V1 to a signal rectifier including transformer T3 and rectifier tube V2. The signal rectifier is connected through a black-white keying-reversal switch SW2 to the trigger circuits which include vacuum tubes V3 and V4 and neon tubes N1 and N2. Switch SW2 is connected across resistor R4 of the signal rectifier output. In its white position switch SW2 connects the negativ end of resistor R4 to 5 ground and connects the positive end of resistor R4 through resistor R6 to the grid of trigger circuit tube V3. In its black position switch SW2 connects the negative end of resistor R4 through resistor R6 to the grid of the tube V3 and connects the positive end of resistor'R4 to a relatively low voltage point ofthe voltage sup! I The plate of vacuum tube V3 is connected through resistor R9 to one electrode of neon tube N1, the other electrode of neon tube N1 being connected through resistor R10 to ground and through a coupling resistor R11 to the grid of vacuum tube V4. The plate of vacuum tube V4 is connected to one electrode of neon tube N2 and the other electrode of the neon tube is connected through resistor R13 to ground and through coupling condenser C5 and resistor R15 to the grid of tube V5 included in the lag circuits. The junction of condenser C5 and the electrode of neon tube N2 are connected through resistor R14 to the cathode of tube V5. I

The lag circuits include vacuum tube V5 and neon tubes" N3 and N4,, a nd also condensers C5, and resistors Rlfi and R11, elements C5, R16 and R11 being used for timing. Qne electrode of neon tube N3 is connected to the plate of vacuum tube V5. The other electrode of neon tube N3'is connected to one electrode of neon tube N4. The other electrode of neon tube N4 is connected througha resistor to B-plus and also through a differentiating circuit comprising condensers C6 and C1 and resistor R20 to the grid of vacuum tube V6 included in the gate circuit. Resistor R11 is variable to allow for lag timing adjustment. I

The gate circuit comprises vacuum tubes V6 and V! connected to form a one-shot multivibrator circuit. Condenser C0 connected between the plate of tube V6 and the grid of tube V1, along with resistor R23 between the plate of' tube V6 and plus-battery, as well as resistors R and R26 connected between the grid of tube V1 and plus-battery, determine the'time characteristics of the gate circuit.- The cathodes of tubes V6 and V1 are connected through variable resistor R11 and resistor R16 to the junction of condenser'C5 and R15; The

cathodes of tubes V6 and V1 are connected through resistors R21 and R22 to ground; r

The frequency multivibrator includes vacuum tubes V0 and V9. The plate of tube V8 is connected through condenser C10 and resistor R34 to the grid of tube V9. The plate of tube V9 is connected through condenser C11 and resistor R to the grid of tube V8 so that a multivibrator is provided. The cathode of tube V8 is connected.

through condenser C9 to'the cathode oftube V1 in the gate circuit The cathode of tube V9 in the frequency multivibrator circuit is connected through resistor R21 to the'cathode of tubeVG in the gate circuit. The gate circuit therefore provides the bias supply to the frequency multivibrator circuit which is so arranged that it is normally quiescent but produces two mutually inverted square waves at the plates of tubes V8 and V9, respectively, during the existence of the gate pulse produced by gate circuit. The first square waves produced by the frequency multivibrator after a quiescent period are always in the same direction.

The junction of resistor R30 and condenser C1 1 is connected through resistor R29 and variable resistor R28 to ground. The junction of resistor R34 and condenser C10 is connected through resistor R33 and variable resistor R32 to ground. The grid of tube V1 is connected through resistor R25 and variable resistor R26 to plus-battery. Variable resistors R26, R28 and R32 have a ganged adjustment for selecting the frequency of the fre- Y quency multivibrator circuit.

One clipper circuit includes a double diode V10, the other clipper circuit includes the double diode V11. In each of double diodes V10 and V1 1, one cathode is connectedt'o one anode. The remaining cathode of each double diode is connected to the junction of resistor R13 and the electrode of neon tube N2 in the trigger circuits. The remaining plates of diodes V10 and V1.1 are connected to ground. The connected plate and cathode of double diode V10 is connected through condenser C12 and resistor R39 to the junction of resistors R35 and R36. The other terminal of resistor R35 is connected to the plate of tube V8 of the frequency multivibrator. The other terminal of resistor R36 is connected to plus-battery. The'connected plate and cathode of double diode V11 is connected through condenser C13 and resistor R40 to the junction of resistors R31 and; R38. The other terminal of resistor R31 is cona one-shot multivibrator circuit. The grid of tube V14 is connected through resistor R56 and variable resistor R58 to plus-battery. The grid of tube V12 is connected to the connected plate and cathode of'double diode tube V10 and to ground through resistor R41. The plate o f tube V14 is connected through the operating coil of relay RYI and resistor'R49 to B-plus. I H

The A regenerator circuit is also a one-shot multivibrator circuit comprising vacuum tubes V13 and V15 which are interconnected with:

double diode tube V11 and relay RY2 in a manner corresponding .to the connections of regenerator circuit"B with double diode V10 and relay RYI. Relay RYI operates contacts'in a channel B-output while relay RY2 operates contacts in the ohannel A-output. It will be obvious that one conventional Teletype printer will be connected to the B-output while another conventional Teletyp'e printer will be connected to the A-output.

' In describing the operation of the device shown in Figs. 2-a. and 2'b, reference will be made to the oscillographs shown in- Fig. 3. The signal.

appearing in the secondary'of transformer T2 is shown at' A in Fig.3. It will be noted that each group of coded pulses'is preceded by an inactive period marked "Stop. The stop periodis-followed by a Start signal of 22 milliseconds. The 5 start signal is followed'byY units of 22,mil1iseconds each. Each of these 5 units together with e 5b P d a e igi equi y into @1537 e portion and an A portion. The pulses'which constitute the B message are transmitted dur Resistor BI is provided so thatv the desired input level of signal can be selected, The, signal indicated at, A is amplified by input amplifier tube VI andrectified bythesignal rectifier to produce groups of coded pulses. and white sweep SW-tube is provided to invert the signal so that the receiver may be used with either"black or white reception.

Since the signal appliedto the input. transformer T2 may be badly distorted, the trigger circuits are provided to produce the square-shaped waves shown at B of. Fig. 3. When the voltage on the grid of tube V3 is relatively high, the tube conducts and the voltage of the plate is relatively low. When the plate of tube V3 is relatively low, the glow in neon tube NI .is extinguished. Conduction through tube N lceases and the grid of tube V4 drops in voltage, lowering the current through the tube V4. This causes-the voltage at the plate of tube V4 to rise and causes ionization in neon tube N2. Similarly, when a relatively low voltage is applied to the grid of tube V3 through the occurrence or lackof pulses in the received signal, the plate of V3 goes up in voltage, causing tube N! to strike. This causes the voltage applied to the grid of tube V4 to rise which produces a relatively low voltage at-the plate of tube V4. This relatively low voltage applied across 1 neon tube N2 causes that tube to be deenergized.

The striking and deenergizingof neon tube N2 causes the voltage across resistor R13 to sharply rise and fall and produce the square waves shown at B in Figs. 2-a and 2-2), which correspond in duration to the modulation on the audio input applied to transformer T2.

differentiated by condenser C5 and its associated circuit and applied through resistor R to the grid of tube V5.

rising pulse transmitted. by condenser C5pulls down'the voltage on the plate of tube V5 for a short time, which results in the extinguishing of neon tubes N3 and N4.

However, as the pulse transmitted by condenser C5 decays in amplitude a' point is reached where neon tubes N3 and N4 again strike. When neon. tubes N3 and N4 strike, the voltage at the electrode of tube N4 connected through a resistor to plus-battery and to condenser C6 will rise.

It will thus be seen that the pulse applied tocondenser C5 by the lag circuits is a square pulse, the leading edge of which corresponds with the rising edge of the square wave shown in B of Fig. 3 but delayed by atime interval equal to the time constant of the lag circuit. The trailing edge of the pulse impressed on the grid of V5 of the lag circuits occurs at a time after the rising edge of the square Wave shown in B of'Fig. 3 by a time fixed by the adjustment of variable resistor Rll. V I

The pulse applied to condenser C6 by the trigger circuits is differentiated by differentiating circuit formed by condenser C6, condenser Cl. and resistor R20. This difierentiating circuit produces The black Resistor Rl5 is provided to prevent over-loading of the grid. of tube V5..

The square waves from the trigger circuits are a first negative sharp when neon tubeslNl and N4 strike, and a second positive sharp' pipwhen these tubes are extinguished.

The gatecircuit, including vacuum tubes-3V5 and V1, is acne-shot multivibrator which started only bythe second, or positive, pip trans-- mitted'by the difierentiating circuit including 618's. ments. C6, C1, and R20. 7 The gate circuit is thus: unbalanced at-a determinable short relay after-the. arrival of the start pulse to produce, a long gate pulse; as shown in C of ,Fig. 3. This gate pulse. lasts toapproximately the end of the 5-units.

The duration ofthis gate puls vistimed by condenser C8, resistor R25 and variable resistor R26. When, the gate circuit multivibrator is in its unbalanced condition and is producing the gate:

pulse shownin C of Fig 3, the cathode "of vacuum tube. ,Va is at a relatively low voltage which is applied through resistors R15, Rlli'andw such that the frequency multivibrator, normally. quiescent, is caused to start oscillating;= The. direct currentcircuit through R2] to V9 is the primary control route from the gate to the 1re-: quency multivibrator circuit. A return route. through C9 is primarily for the pips fromthe frequency. multivibrator to aid in shuttingdown;

the gate circuit. The frequency .multivibrator. including. tubes V8 and V9 produces two mutually inverted squarewaves, one of which: is shown at Df in Fig. 3. The period of the frequency multi--v vibrator is fixed by variable resistors 28 and-32 so that a frequency is produced closely approximating that of the incoming coded pulses.

.A series of. sharp pips are applied througheondenser C9 to the cathodeof. tube V! of the gate multivibrator. When the multivibrator is in its unbalanced condition and is producing the gate pulse, the condenser C8 is slowly dischargingv to a point wherethe multivibrator will returnto its; balanced condition. The series of sharp'pips are applied through condenser C9, sothat the gate multivibrator will return toits balanced condition and the gate pulse will end in time coincidence.

with one ofthe pips transmitted through cone denser C9 and in synchronism with. thetrailing edge of one of the square waves produced lay-thev frequency multivibrator.

One of the square waves produced by the fre-' quency multivibrator is applied through voltage divider comprising resistors R35 and R36 through isolating resistor R39 and throughv condenser C12 to the connectedcathode and plate of double"- Condenser CIZ cannot transmit a:

diode VH7. downwardly extending pip at each downwardly extending edge of the square wave produced by the frequencymultivibrator because the plate of double diode VHl connected to ground eliminates I thesedownwardly' extending pips; .Conde'nser Cl 2 can only. transmit an upwardly extending pip; as seen at E in Fig. 3 at each rising edge ofthe square wave produced by the frequency multivibratorwhen a positive'biasis applied by "the incoming signal shown at Bin Fig. 3 totthe cathode of the double diode of V10 connected'to the trigger circuits.

The operation of double diode V! l with respect to the square wave impressed upon it through condenser CIS and with respect to the signal applied from the trigger circuits is similar to that described above for the circuits including double diode W0. It is thus seen that there is applied to theigrid of tube VIZ of regenerator circuit B a sharp positive pip whenever there is a received pulse existing in time coincidence with a leading edge of the square wave produced by the frequency multivibrator. Similarly, there is applied to the grid of tube VI 3 of regenerator circuit A, as seen at G" in Fig. 3, an upwardly extending pip whenever there exists a received pulse in timeregistry with the upwardly rising edge of the inverted square wave supplied by the frequency multivibrator and applied to double diode VI I.

The pips applied to grid of the tube VIZ cause the one-shot multivibrator including tubes VH and VIA to produce a square pulse. The oneshotinultivibrator comprising tubes W2 and VM which constitutes the B regenerator circuit has a natural frequency equal to the one whole unit or 22 milliseconds. The output of the multivibrator VIZ, VH4, operates relay RYl which in turn operates the conventional Teletype printer attached thereto. The voltage applied to the operating coil of relay RYI is the upper plot marked F in Fig. 3 while the opening and closing ot the contacts of relay RY2 is shown in the lower plot marked F in Fig. 3.

The operation of the A regenerator circuit is similar to that described above for the B regenerator circuit. Plots showing the voltage applied to the operating coil of relay RY2 and the opening and closing of the relay contacts are shown in H" of Fig. 3.

It will thus be seen that the device described above operates to separate the A" pulses from the B pulses and deliver them to their respective outputs, and also lengthens them to double their original length, a duration usuable by the conventional Teletype machine.

The regenerator circuit may take the form of a one-shot multivibrator as shown in Fig. 2, where the time it is unbalanced is the desired time for a unit of the output regenerated Baudot code. The cathode or plate circuit of one tube may be the output channel. In the action of the regenerator, when it is a one-shot multivibrator, the regenerated time is slightly shorter than the desired time in order to allow the one-shot multivibrator to restore itself to original condition prior to the time the next actuating pip is received. Where a relay is used in the output, the make and break time intervals of the relay may be 50 adjusted that their difierence may be additive to the regenerated signal and of proper length to extend the regenerated signal to the exact desired length.

For single channel operation, only one output circuit need be used and the lag circuit adjusted for normal positioning for the sampling pips in the center of the units of the received signal. For diplex operation, both output circuits are used. And similarly, the lag circuit is adjusted for approximately one-half of the lag normally used for simplex operation in order that the sampling pips occur in the center of the diplex signal units which are one-half the length of those for a simplex signal.

The necessary synchronism between the distributor and the transmitting apparatus is achieved because the frequency multivibrator is adjusted to approximately the frequency of the incoming signals. Adequate synchronism is assured because the multivibrator is started at the beginning of each 5-units in synchronism with the received group of pulses.

The principles embodied in the circuits described above are not restricted to just diplex operation of a system using S-digit Baudot code. They can be applied to simplex circuits as a regenerative repeater or to multi-channel operation. They are also applicable to any start-stop code.

The lag circuit in the device described above may alternatively consist of a one-shot multivibrator or similar circuit wherein the circuit when actuated will deliver a pulse at any predetermined time thereafter as adjusted by a variable control. If the lag circuit includes a one-shot multivibrator, the multivibrator is arranged to be quiescent in one condition but to respond to a pulse from the trigger circuit to produce a square wave of adjustable length. The trailing edge of this square wave may be diil'erentiated by a circuit similar to that including elements C6, C1, and R20 and the resulting pulse used to energize the gate circuit. The duration of the square wave then determines the delay introduced by the lag circuit.

The specific devices described above are by way of example, and many modifications and changes therein will occur to those skilled in the art within the scope of the appended claims.

What is claimed is:

1. In a receiving keyer including means to receive groups of a predetermined number of coded pulses, a lag circuit to produce a delayed pulse in response to a received pulse, said lag circuit being connected to said receiving means and provided with adjustable means connected to said lag circuit to vary the period by which the delayed pulse follows the received pulse, a normally quiescent electronic oscillator connected to said lag circuit and arranged to produce a wave of a predetermined number of cycles on production of said delayed pulse, said number of cycles corresponding approximately to said predetermined number of coded pulses in a group, and means to produce an output pulse only when a received pulse occurs in coincidence with a predetermined point in said cycles.

2. The combination of claim 1, in which means are provided to regenerate said output pulse to a predetermined shape and time duration.

3. The combination of claim 1, in which means including a one-shot multivibrator are provided to regenerate said output pulse to a predetermined shape and time duration.

4. In a telegraphic keyer, a lag circuit to produce a delayed pulse in response to a received pulse, adjustable means connected to said lag circuit to selectively vary the period by which the delayed pulse follows the received pulse, a gate circuit connected to said lag circuit and arranged to produce a gate pulse of predetermined length in response to said delayed pulse, means to prevent the application of a delayed pulse to said gate circuit during the existence of said gate pulse, a normally inoperative oscillator of adjustable frequency connected to said gate circuit and energized by said gate pulse only during'the existence thereof, means to produce a series of sampling pulses, said pulses each occurring at a predetermined point in the cycles of said oscillator, means to produce an output pulse when a sampling pulse occurs in coincidence with a received pulse.

5. In a telegraphic keyer, a lag circuit to produce a delayed pulse in response to a received pulse, adjustable means connected to the lag circuit for selectively varying the period by which the delayed pulse follows the received pulse, a gate circuit connected to said lag circuit to produce a gate pulse of predetermined length in response to said delayed pulse, a normally quiescent oscillator of adjustable frequency connected to said gate circuit and energized by said gate pulse, means for producing output pulses of one series when a received pulse occurs during half-cycles of one polarity of said wave produced by said oscillator, means for producing output pulses of another series when a received pulse occurs during half-cycles of the other polarity of the wave produced by said oscillator.

6. In a telegraphic keyer, a lag circuit to produce a delayed pulse in response to a received pulse, adjustable means connected to said lag circuit to vary the period by which the delayed pulse follows the received pulse, a gate circuit connected to said lag circuit to produce a gate pulse in response to said delayed pulse, a source of a series of square waves energized by said gate pulse, means for producing two series of sampling pulses, one series of sampling pulses being in time coincidence with the leading edge of the square wave, the other series of sampling pulses being in time coincidence with the trailing incidents of said square waves, two regenerator circuits each connected to one series of sampling pulses and arranged to produce a pulse -of predetermined length in response to the simultaneous reception of a sampling pulse and a received pulse.

7. In combination, means to receive a carrier wave modulated by groups of coded pulses, means to rectify said received wave to produce a group of coded pulses, trigger circuit means to reshape said group of coded pulses into a group of square coded pulses, a gate circuit to produce a gate pulse of an approximate predetermined length, a lag circuit for producing a gate trigger pulse at a selectively variable time after the arrival of a first pulse of a group, means to apply said gate trigger pulse to said gate circuit to produce said gate pulse, means to disable said lag circuit from producing gate trigger pulses during the existence of said gate pulse, a normally quiescent source of two series of square waves of adjustable frequency each of said series of square waves being inverted with respect to the other, means for applying said gate pulse to said source of square waves to operate said source during the existence of said gate pulse, means for producing sharp pulses occurring in time registry with the trailing edges of one of said series of square waves to cause said gate pulse to terminate in synchronism with one of said trailing edges, a difierentiating circuit to differentiate each of said square waves to produce a series of positive and negative sampling pips corresponding to each square wave, clipping means to eliminate from each series of sampling pips, pips of one polarity, biased clipping means biased by said groups of pulses to eliminate pips of the other polarity except when a coded pulse occurs in registry with said pip, two regenertor circuits, each including a square wave generator arranged to produce When energized one square wave of a predetermined length, means for applying the unclipped sampling pips of each series to one of said regenerator circuits.

8. In a receiving keyer, a lag circuit responsive to received signals for producing pulses corresponding to said received signals but delayed with respect thereto, means for selectively varying the amount of said delay, a normally quiescent oscillator for producing an electrical wave having cycles of a predetermined length, gate means responsive to said delayed pulses and connected to cause said oscillator to produce a predetermined number of said electrical wave cycles upon receipt of a delayed pulse, means to prevent said gate means from initiating production of said predetermined number of cycles of said electrical wave when said oscillator is operating, means connected to said oscillator to produce a series of sampling pulses, one of said sampling pulses being produced at one predetermined point in each cycle of said electrical Wave during said predetermined number of cycles, and means to produce an output pulse at one output when a sampling pulse occurs in accordance with a received pulse.

9. The combination of claim 8 additionally characterized by means connected to said oscillator for producing a second series of sampling pulses, each of said second series of sampling pulses being produced at a difierent predetermined point in each cycle of said electrical wave during said predetermined number of cycles, and means to produce an output pulse at a second output when one of said second series of said sampling pulses occurs in coincidence with a received pulse.

GENE L. BREWER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date L 2,365,450 Bliss Dec. 19, 1944 2,415,359 Loughlin Feb. 4, 1947 2,422,205 Meacham June 17, 1947 2,426,216 Hight Aug. 26, 1947 2,430,547 Anderson Nov. 11, 1947 2,474,490 Pelle June 28, 1949 2,484,066 Bacon Oct. 11, 1949 OTHER REFERENCES A New Electronic Telegraph Regenerative Repeater, by Ostendorf, Electrical Eng, vol. 69, Issue 3, page 237-240, March 1950. 

